How do I open my .blend file as a folder?
You can't.

blender files use a custom binary format for a lot of stuff, so you really need to open blender to modify them safely.

There is a bit more information here:
How would you go about reading a .blend file? I mean all of a .blend file, not just the .obj information

The best way to achieve similar functionality would be to do it as an addon within blender, so blender can handle file operations.